1. Field of the Invention
The present invention relates to a cooling system and a cooling method, and particularly, to a cooling system and a cooling method for cooling a motor which drives a compressor in a cooling system having a compressor for compressing refrigerant.
2. Description of the Background Art
FIG. 1 is a block diagram showing a structure of a cooling system.
Generally, a cooling system constructing a closed system comprises: a compressor 10 for compressing working fluid such as refrigerant; a condenser 20 for condensing the refrigerant compressed in the compressor 10; an expansion means 30 for lowering pressure of refrigerant condensed in the condenser 20; and an evaporator 40 for evaporating the refrigerant of liquid state which is expanded in the expansion means 30, as shown in FIG. 1.
The cooling system is applied for storing food or for maintaining indoor environment to be pleasant using warm air or cool air generated in the condenser and in the evaporator.
On the other hand, in the refrigerant system, the compressor for compressing the refrigerant is required to increase an output, or to have a large output as a size thereof is reduced according to objects of usage.
As an example, in case that a turbo compressor, which compresses the refrigerant by rotation of an impeller which is a kind of centrifugal compressors, is used in the cooling system such as an air conditioner, a relatively smaller compressor is used. In addition, in order to reduce the size of the turbo compressor, the size of the impeller should be reduced. And in order to maintain an output more than a predetermined level, the impeller should rotate at high speed relatively. Consequently, a motor for rotating the impeller should rotate at high speed.
However, when the motor rotates at high speed in order to increase output of the compressor or to reduce the size of the compressor, a lot of heat is generated from the motor. The generated heat of high temperature may damage the motor, or may damage components around a motor mounting chamber. Therefore, the motor should be cooled down in order to be operated as maintaining stable state continuously.
FIG. 2 is a cross-sectional view showing a turbo compressor which is one of compressors used in the cooling system shown in FIG. 1.
U.S. Pat. No. 6,009,722 suggests a structure for cooling a motor as a method for cooling the motor of the turbo compressor used in the cooling system.
According to U.S. Pat. No. 6,009,722, the turbo compressor comprises a motor mounting chamber C, in which the motor M is mounted, formed inside a casing 11, and a first and a second compression chambers C1 and C2 disposed on both sides of the motor mounting chamber C, as shown in FIG. 2.
In addition, the first and second compression chambers C1 and C2 are located on both sides of the motor M, and a first and a second impellers 13 and 14 are coupled to both ends of a rotational shaft 12 of the motor.
A suction pipe P1, which is connected to an evaporator 40 so that the refrigerant of low pressure has passed an evaporating process in the evaporator 40 can be flowed into the motor mounting chamber C, is coupled to the casing 11, a first connection flow path F1 for communicating the motor mounting chamber C and the first compression chamber C1 so that the refrigerant gas passed through the motor mounting chamber C can be flowed into the first compression chamber C1 is disposed, and a second connection flow path F2 for communicating the first compression chamber C1 and the second compression chamber C2 so that the refrigerant gas compressed firstly in the first compression chamber C1 can be flowed into the second compression chamber C2 is disposed.
In addition, an exhaust pipe P2 for guiding the refrigerant gas which has compressed secondly in the second compression chamber C2 to be exhausted toward the condenser 20 comprised in the cooling system is coupled to the casing 11 so as to communicate with the second compression chamber C2.
In the turbo compressor having the above structure, when the motor M is rotated by being applied electric current, the rotational force is transmitted to the first and the second impellers 13 and 14 through the rotational shaft 12 to rotate the first and second impellers 13 and 14 inside the first and second compression chambers C1 and C2 respectively. As the first and second impellers 13 and 14 rotate in the first and second compression chambers C1 and C2 respectively, the refrigerant of low temperature and low pressure state which has passed through the evaporator is flowed into the motor mounting chamber M through the suction pipe P1 by a pressure difference generated in the first and second compression chambers C1 and C2. And the refrigerant gas flowed into the motor mounting chamber C is sucked into the first compression chamber C1 through the first connection flow path F1 as passing through the motor mounting chamber C, and compressed firstly in the first compression chamber C1.
The refrigerant gas compressed firstly in the first compression chamber C1 is flowed into the second compression chamber C2 through the second connection flow path F2, and is compressed secondly in the second compression chamber C2. And the refrigerant gas of high temperature and high pressure state compressed secondly in the second compression chamber C2 is exhausted through the exhaust pipe P2, and the exhausted refrigerant gas is flowed into the condenser 20 which consists of the cooling system.
Especially, the refrigerant gas of low temperature and low pressure state which has passed through the evaporator 40 is flowed into the motor mounting chamber C through the suction pipe P1, meanwhile, the refrigerant gas cools down the motor by sucking the heat generated from the motor M.
However, the structure for cooling motor is not able to cool down sufficiently the heat generated from the motor M, and especially, the motor M may be damaged if an overloaded state is maintained. Also, the refrigerant gas sucked into the first compression chamber C1 is sucked as passing through the motor mounting chamber C, and therefore, the refrigerant gas is sucked in heated state and a specific volume of the refrigerant gas is reduced. Therefore, the compressing efficiency is also reduced.
Therefore, an object of the present invention is to provide a cooling system which is able to cool down heat of high temperature which is generated from a motor of a compressor while the compressor used in a cooling system is operated.
To achieve the object of the present invention, as embodied and broadly described herein, there is provided a cooling system including a motor cooling means which cools down the motor by making some of refrigerant passed through a condenser flow to the compressor, wherein the cooling system comprises a compressor for compressing the refrigerant by operation of the motor.
Also, there is provided a cooling system, which comprises a compressor for compressing refrigerant by an operation of a motor, a condenser, an expansion means, and an evaporator, for cooling down the motor by making some of refrigerant passed through the condenser flow to the compressor.
Also, there is provided a cooling method which measures a temperature of a motor, and cools down the motor by injecting refrigerant which has passed through the condenser when the temperature of the motor is higher than a set temperature, in a cooling system comprising a compressor for compressing refrigerant by an operation of a motor, a condenser, an expansion means, and an evaporator.